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Special Effects and Game Development in Java(TM) - Your first applet

by Anibal Wainstein

2.0 Your first applet

Now it is time to start programming your first applets. It is always a great experience to see your first creations in action.

2.0.1 Inheriting the Applet class 

We have earlier described what an applet is. In Java there is already a finished class called "Applet". This is used as the parent class (the base) for all the types of applets that you create. To do our own applet, we will overwrite some of the methods in it and put extra variables. This is called in Object Oriented Programming to inherit the Applet class.

import java.applet.*;
import java.awt.*; public class myapplet extends Applet { }

I know that this was a lot at once but we can start by describing "import" that makes sure that you have access to the Applet class and the AWT package. In the AWT package there is the class String and other important classes that you may need when you make applets. This is called importing a Java class package. The "public" declaration indicates that the applet will be able to be used by other classes (this is something that is necessary to have with some Java VM's). The "class" declaration indicates that the applets name will be "myapplet". The "extends" declaration means that the class "myapplet" will inherit the Applet class methods. The applet do not do anything right now, because we have not yet made any changes on the parent class.

2.0.2 Initializing with the init() method and how to write strings.

The first change we will do on our applet is to overwrite the init() method. This method is the first method executed in an applet.

import java.applet.*;
import java.awt.*; public class myapplet extends Applet { public void init() {
    System.out.println("Hello Sweden!"); } }
Here we use the built-in method println() (print-line) that exist in the class "out", which in turn exist in the Java package "System". With this we write the string "Hello Sweden!" on the Java console. The Java console is the communication window with the programmer, which you can display with your web browser when you test the applet. By using it, we can receive applet error messages and display our own messages like "Hello Sweden!".


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